lkml.org 
[lkml]   [2003]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Benefits from computing physical IDE disk geometry?
    Chuck Ebbert wrote:

    >>If RAID1 can use the generic elevator then it should. I
    >>guess it can't though.
    >>
    >
    >
    > No, but it is feeding IO requests into the elevators of the
    >block devices below it. For a given read, all it wants to do
    >is pick one device to handle the work. If it could look into
    >the queues maybe it could make better decisions.
    >
    OK right. As far as I can see, the algorithm in the RAID1 code
    is used to select the best drive to read from? If that is the
    case then I don't think it could make better decisions given
    more knowledge. It really wants to know if the disk head is
    close to request x however it is impossible to tell where the
    disk head will be by the time request x is the next in line
    for that disk, regardless if it can look at the low level
    queues or not.

    It seems to me that a better way to layer it would be to have
    the complex (ie deadline/AS/CFQ/etc) scheduler handling all
    requests into the raid block device, then having a raid
    scheduler distributing to the disks, and having the disks
    run no scheduler (fifo).

    In practice the current scheme probably works OK, though I
    wouldn't know due to lack of resources here :P

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 13:34    [W:0.108 / U:88.960 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site